appcore-provider

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appcore-provider defines how a Deployment Manifest selects concrete Runtime infrastructure without making contract crates depend on implementations. It owns provider roles, construction plans, factories, secret resolution, generic coordination stores, fenced shared leases, and job-provider contracts.

Composition flow

1. A deployment declares provider IDs and settings.
2. The composition root registers explicit ProviderFactory implementations in ProviderRegistry.
3. DeploymentProviderPlan validates that each required ProviderRole has exactly one usable provider.
4. The factory receives a bounded ProviderContext and resolved secret owners, then returns the requested implementation.

Missing or invalid providers stop bootstrap. The registry never substitutes a provider silently. ResolvedSecret zeroizes its owned bytes and must not be copied into diagnostics.

use appcore_provider::{
    CoordinationStoreProvider, InMemoryCoordinationStore, ProviderResult,
};

fn check_coordination() -> ProviderResult<u64> {
    let store = InMemoryCoordinationStore::default();
    store.ensure_compatible()?;
    store.schema_version()
}

Coordination and lease guarantees

The in-memory coordination store is for embedded/test control planes. The file store uses schema V2, atomic replacement, and a 4 KiB metadata/restore-source limit. Readers check length before allocation, retain a sentinel byte to detect growth, and reject symlinks, non-regular files, invalid UTF-8, and corrupt records.

Filesystem leases persist a per-resource epoch high-water sidecar before publishing an active lease. Release never resets the fencing sequence. A token protects a write only when the writer checks the current epoch immediately before that write; filesystems without reliable locks, rename, directory sync, or cache coherence cannot provide strong split-brain protection.

Provider-specific SDK code belongs in an integration crate, not here. See the basic example, the intermediate example, and the crate guide.

cargo test -p appcore-provider

Stable documentation

Stable ID: ACR-019. See the supplemental architecture and integration guide. This permanent ID remains valid if the wiki page moves.